1. Field of the Invention
The present invention relates to a parts suction head having a non-contact sealing structure, and in particular to an improved parts suction head having a non-contact sealing structure which can precisely control rotation of a rotation shaft in a surface mount device.
2. Description of the Background Art
In general, a surface mount device is used to rapidly precisely mount a plurality of parts on a printed circuit board. The surface mount device for rapidly precisely mounting parts on the printed circuit board includes an X-Y gantry, a printed circuit board conveyor, a parts feeder and a head unit. The head unit is installed in the X-Y gantry, for mounting the parts on the printed circuit board transferred to a parts mounting operation position by the printed circuit board conveyor. The head unit receives the parts from the parts feeder to be mounted on the printed circuit board.
The head unit adsorbing the parts supplied from the parts feeder includes a plurality of parts suction heads. Each of the respective parts suction heads includes a motor, a ball spline and a socket unit. The parts suction head composed of a motor, a ball spline unit and a rotation shaft unit will now be described in detail with reference to the accompanying drawings.
FIG. 1 is a side view illustrating a conventional parts suction head of a surface mount device. Referring to FIG. 1, the parts suction head includes a motor 10, a ball spline unit 20 and a rotation shaft unit 30. A rotation central axis 11 of the motor 10 is connected to one end portion of the ball spline unit 20 by a coupling 1. The other end portion of the ball spline unit 20 is connected to the rotation shaft unit 30. The ball spline unit 20 connected to the rotation shaft unit 30 includes a ball spline 21 and a ball spline nut 22. The ball spline unit 20 performs a rotation movement due to a rotary force generated by the motor 10, and performs reciprocation in a vertical direction. When the parts suction head is moved in a vertical direction, the ball spline unit 20 prevents a load of the motor 10 from being transmitted to the rotation shaft unit 30.
The rotation shaft unit 30 connected to the other end portion of the ball spline unit 20 performing the rotation movement and the reciprocation includes a rotation shaft 31, a socket 32, an LM guide 33, a moving block 34 and flanges 35. The socket 32 is installed at one end portion of the rotation shaft 31, and the moving block 34 is disposed at the outer portion thereof. The flanges 35 are provided to both end portions of the moving block 34. Here, the rotation shaft 31 is assembled in the moving block 34. The LM guide 33 is positioned on the rear surface of the moving block 34 in order to vertically reciprocate the rotation shaft 31 assembled in the moving block 34.
The LM guide 33 guides the vertical reciprocation of the rotation shaft 31, the ball spline 21 and the moving block 34, so that the parts suction head of the rotation shaft 31 can suck the parts and mount it on the printed circuit board. When the parts to be mounted on the printed circuit board is not precisely sucked to the parts suction head, the rotation shaft 31 is rotated by the motor 10 in a predetermined radius, thereby correcting suction of the parts.
The structure of the conventional rotation shaft unit 30 correcting the suction of the parts by rotating the rotation shaft 31 will now be explained with reference to FIG. 2. FIG. 2 is a cross-sectional view illustrating the conventional rotation shaft unit having the contact sealing structure in FIG. 1. As depicted in FIG. 2, when the rotation shaft 31 is inserted into the moving block 34, both end portions of the moving block 34 are sealed up by a sealing material 36 to prevent pressure reinforcement from being generated due to external air inputted from both end portions of the moving block 34. Here, air is flowed in and out in an arrow A direction through an air passage 34a of the moving block 34, and a hollow unit 31a and an air passage 31b of the rotation shaft 31 so as to generate a pressure for the parts suction.
The conventional rotation shaft has the contact structure. That is, the rotation shaft is inserted into the moving block, and both end portions of the moving block are sealed up by the sealing material. Accordingly, when the rotation shaft is rotated, a non-linear frictional force is generated between the sealing material containing rubber and the rotation shaft. In the case that the rotation shaft is precisely rotated, it is impossible to stabilize a rotation angle in a wanted time due to the non-linear frictional force.
Accordingly, it is a primary object of the present invention to provide a parts suction head having a non-contact sealing structure which can prevent a non-linear frictional force from being generated in rotation of a rotation shaft inserted into a moving block in a rotation shaft unit of a surface mount device.
It is another object of the present invention to stabilize rotation of a rotation shaft in a wanted time in precise rotation, by rotating a moving block and a rotation shaft in a non-contact type in a parts suction head.
In order to achieve the above-described object of the invention, there is provided a parts suction head having a non-contact sealing head comprising: a moving block having a plurality of first air passages on its upper surface and having a first hollow unit in a longitudinal direction; a spacer having at least one or more second air passage connected to the first air passage for air flow, and having a second hollow unit in a longitudinal direction; a rotation shaft being inserted into the second hollow unit of the spacer at a predetermined interval and having at least one or more third air passage connected to the second air passage for air flow, and having a third hollow unit in a longitudinal direction; and flanges mounted to both end portions of the moving block to seal up an interval between the spacer and the rotation shaft.